How do i get a referral letter for covid-19 test?

Call Health Dept: Many advise checking with your doc which is fine, however, your local Dept. of Health likely has information many doctors don't such as hours/locations of testing centers as well as types of patients seen (i.e. walk-ins, drive-ups, etc). They can also tell you if your state requires a primary doc's referral. Most states don't force PMD referral for COVID19 testing, BUT some do.